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Tuesday, August 7, 2018

Hydrographic Surveying – Methods, Applications and Uses

Hydrographic surveying or bathymetric surveying is the survey of physical features present underwater. It is the science of measuring all factors beneath water that affect all the marine activities like dredging, marine constructions, offshore drilling etc.

Hydrographic surveying is mainly conducted under authority concerns. It is mainly carried out by means of sensors, sounding or electronic sensor system for shallow water.

The information obtained from hydrographic surveying is required to bring up nautical charts which involves,

Available depths
Improved Channels
Breakwaters
Piers
The aids to navigation harbor facility

These survey also take part in necessary data collection relating to construction and developments of port facilities, such as pier construction. This help in finding the loss in capacity due to silt and many uncertainties.

Hydrographic Surveying - Methods, Applications and Uses

Applications of Hydrographic Surveying

Following are the applications of hydrographic surveying:

Dock and Harbor Engineering
Irrigation
River Works
Land reclamation
Water Power
Flood Control
Sewage Disposal

Uses of Hydrographic Surveying

Uses of hydrographic surveying are given below:

Depth of the bed can be determined
Shore lines can be determined
Navigation Chart Preparation
Locate sewer fall by measuring direct currents
Locating mean sea level
Scouring, silting and irregularities of the bed can be identified
Tide measurement
River and stream discharge measurement
Massive structures like bridges, dams harbors are planned

Preliminary Steps in Hydrographic Surveying

The method starts by locating special control points along the shore line. The sounding method is employed to determine the depth at various points by means of stationary boats. Sounding locations can be either made from boat to the control points or by fixing a point in the boat and taking sounding from the control point. Before this procedure certain preliminary steps have to be made:

Reconnaissance
Locate Horizontal Control
Locate vertical Control

Reconnaissance

As every project require a start-up plan to complete it effectively and economically, reconnaissance has to be undergone. A complete reconnaissance of whole survey area to choose the best way of performing the survey.

This would facilitate satisfactory completion of the survey in accordance with the requirements and specifications governing such work. Aerial photographs would help this study.

Locating Horizontal Control

The horizontal control is necessary to locate all features of the land and marine in true relative positions. Hence a series of lines whose lengths and azimuths are determined by means of either triangulation or any other methods.

Tachometric and plane table survey can be conducted in order to undergo rough works. No rules are kept for establishing horizontal control as topography, vegetation, type, size of topography affect the rules.

But in general a rules can be kept for type of control say:

It is advisable to run traverses along each shore, connecting each other by frequent tie lines –If water body > 1km wide
It is advisable to run transverse line only along one of the banks -If water body is narrow
Triangulation system -If shorelines filled by vegetation
Large network of triangulation system for large lakes and ocean shore lines

A combined triangulation and traversing is shown in figure 1.

Locating Vertical Control

Before sounding establishment of vertical control is essential to determined. Numerous benchmarks are placed in order to serve as vertical control. Setting and checking the levels of the gauges are uses of benchmarks

Fig. 1: Combined Triangulation and Traversing in Hydrographic Survey

Sounding in Hydrographic Survey

The process of determining depth below water surface is called as sounding. The step before undergoing sounding is determining the mean sea level. If the reduced level of any point of a water body is determined by subtracting the sounding from mean sea level, hence it is analogous to levelling.

The specific need for sounding are

1. Preparation of navigation charts that is an all-time information for future purpose also

2. Material that to be dredged has to be determined early to facilitate easy movement in project without any confusion

3. Material dredging should also accompany where filling has to be done. Material dumping is also measured

4. Design of backwaters, sea wells require detailed information that is obtained from sounding

Equipment for Sounding

The essential equipment used for undergoing sounding are

Shore signals and buoys
Sounding Equipment
Instruments for measuring angles

The explanations are given below

1. Shore signal and buoys

These are required to mark the range lines. A line perpendicular to shore line obtained by line joining 2 or 3 signals in a straight line constitute the range line along which sounding has to be performed. Angular observations can also be made from sounding boats by this method. To make it visible from considerable distance in the sea it is made highly conspicuous.

A float made of light wood or air tight vessel which is weighted at bottom kept vertical by anchoring with guywires are called buoys. In order to accommodate a flag a hole is drilled. Under water deep, the range lines are marked by shore signals & the buoys.

2. Sounding Equipment

The individual units involved are explained one by one:

a. Sounding boat

A flat bottom of low draft is used to carry out sounding operation. Large size boats with motor are used for sounding in sea. The soundings are taken through wells provided in the boat. A figure depicting sounding boat is shown in fig.2.

Fig.2: Sounding Boat

b. Sounding pole or rod

Rod made of seasoned timber 5 to 10cm diameter and 5 to 8m length. A lead shoe of sufficient weight is connected at bottom to keep it vertical. Graduations are marked from bottom upwards. Hence readings on the rod corresponding to water surface is water depth.

c. Lead line

A graduated rope made of chain connected to the lead or sinker of 5 to 10kg, depending on current strength and water depth. Due to deep and swift flowing water variation will be there from true depth hence a correction is required.

Fig.3.Sounding Pole and Lead line

Other sounding equipment used are Weddell’s sounding machine. These are employed when large sounding work has to be undergone. A standard machine to measure maximum of 30 to 40m is designed that are bolted over the well of the sounding boat.

Another equipment used is fathometer which is an echo-sounding instrument used to determine ocean depth directly. Recording time of travel by sound waves is the principle employed. Here the time of travel from a point on the surface of the water to the bottom of the ocean and back is recorded.

Knowing the velocity of sound waves the depth can be calculated as shown in fig.4.

Fig.4: Echo Sounding in Hydrographic Survey

From the above figure the depth D can be calculated if AB can be found. This method gives truly vertical and accurate methods. It is found more sensitive than a lead line.

6 Types of Deep Foundations used in Construction and Their Uses

Deep foundation is required to carry loads from a structure through weak compressible soils or fills on to stronger and less compressible soils or rocks at depth, or for functional reasons. Deep foundations are founded too deeply below the finished ground surface for their base bearing capacity to be affected by surface conditions, this is usually at depths >3 m below finished ground level.

Deep foundation can be used to transfer the loading to a deeper, more competent strata at depth if unsuitable soils are present near the surface.

Types of Deep Foundation

The types of deep foundations in general use are as follows:

Basements
Buoyancy rafts (hollow box foundations)
Caissons
Cylinders
Shaft foundations
Pile foundations

1. Basement foundation

These are hollow substructures designed to provide working or storage space below ground level. The structural design is governed by their functional requirements rather than from considerations of the most efficient method of resisting external earth and hydrostatic pressures. They are constructed in place in open excavations.

2. Buoyancy Rafts (Hollow Box Foundations)

Buoyancy rafts are hollow substructures designed to provide a buoyant or semi-buoyant substructure beneath which the net loading on the soil is reduced to the desired low intensity. Buoyancy rafts can be designed to be sunk as caissons, they can also be constructed in place in open excavations.

3. Caissons Foundations

Caissons are hollow substructures designed to be constructed on or near the surface and then sunk as a single unit to their required level.

Types of Deep Foundation - Caisson Foundation

4. Cylinders

Cylinders are small single-cell caissons.

5. Drilled Shaft foundations

Shaft foundations are constructed within deep excavations supported by lining constructed in place and subsequently filled with concrete or other pre-fabricated load-bearing units. Read more on drilled shaft foundation

6. Pile foundations

Pile foundations are relatively long and slender members constructed by driving preformed units to the desired founding level, or by driving or drilling-in tubes to the required depth – the tubes being filled with concrete before or during withdrawal or by drilling unlined or wholly or partly lined boreholes which are then filled with concrete.

Saturday, August 4, 2018

Roles and Responsibilities of Structural Design Engineers in Construction

Structural design engineer performs various roles and responsibilities in a construction project providing technical details for the activities to be performed at construction site.

Structural engineering is a wider discipline under the field of civil engineering. It is a vast topic with unlimited theories and practices. It’s a field that is still developing with huge innovations and ideas.

So being a structural engineer, the roles and responsibilities that have to be received is of greater importance.

Roles and Responsibilities of Structural Design Engineers

The structural engineering is more concerned with the design and the physical integrity of the structures. These structures can be buildings, dams, tunnels, bridges etc.

The main focused responsibility of a structural engineer is to bring a structure that will ensure safety and durability till the service period.

The architects develop building only based on the size, shape and use of the building. But these have certain hidden technical issues during construction and after, that can be found and resolved only by the structural engineers. The structural engineers help the architects to achieve his or her vision of the project planned.

Working Times and Location of a Structural Engineer

When looking into the working time and the place spent by the structural engineers, most of the highly involved structural engineers will be working in office as well as on the construction sites.

They can work by splitting the time between both the contexts. The locations of work vary based on the working environments. Rural or metropolitan areas have different working schedules and environment.

The structural engineers may have to work for long hours sometimes similar to site engineers, which mainly depend on the size of the project and the size of the organization.

If the structure of the organization is well defined and large, it will have sufficient members for the design team, planning team, execution team with a group of professionals, skilled as well as semi-skilled employees and workers. This will reduce some burden on the structural engineer.

An organization with a single experienced structural engineer will have to assist the work throughout the course of the project.

Roles and Responsibilities of Structural Design Engineers in Construction

A strong knowledge of physics, creative problem solving and three-dimensional conceptual skill must be gained by a structural engineer. Other than these, the roles and the responsibilities of the structural engineer includes:

Structural Designing
Site and Work Investigations
Communication
Construction Management
Adequate Training

Structural Designing

Structural engineers are more graduated for structural detailing and their analysis. So, they are more in to design of structures. The structural designing procedures carried out by the structural engineers include calculating the loads and the stresses acting on the building, analysis for the loads, design of sections of structures to sustain the loads; so that the structure designed will withstand the loads predicted safely.

The structural engineers are also involved in the selection of materials best suited for the structure. This will hence ask for good knowledge about the different materials that are used in the construction at the current condition like their economic factors, strength factors and durability factors.

The quality factors of different building materials can be analyzed by a structural engineer to finalize their suitability in the design of the beams, columns or the foundations.

Another skill of a structural designer is the analysis of structures. This is presently carried out by the software like ETABS, STAAD, SAP etc. As years pass new software are being developed for the analysis of structures at different conditions of loads like wind, earthquake etc.

Most of the structural engineers have to study and work with these software with a knowledge of both the technical details and the programming details. In some organizations, the analysis is carried out by a programmer who may not have the civil engineering graduation but is assisted by a structural engineer.

Whatever be the mode of analysis done, the structural engineer must have the ability to understand and interpret the results from the software to know the validity of the values provided as output. Some organization won’t completely rely on the computer results, they conduct a separate man-made calculation for assurance.

Site Investigations

When dealing with the site investigation, the structural engineers are involved in checking the condition of the soil for the construction of the project. Based on the loads calculated by the designer, it must be checked whether the soil is suitable to bear the calculated loads.

This investigation will also decide the foundation systems that must be used for the structure. Any kind of treatment required for the soil too is decided based on the investigation. This investigation is carried out by testing the soil which is the part of geotechnical engineer.

Communication

Even though structural engineers are the ones that bring and develop the design ideas and detail, he can only see it happen on the site only if the structure is constructed as desired. For this, his interpretation and ideas have to conveyed with the other members of the projects.

The structural engineer has to coordinate and consult other members like the site engineers, other design engineers, geotechnical engineers, landscape architects, architects, project managers etc. Proper knowledge helps in spreading correct information among the group avoiding confusion and errors.

Construction Management

The management responsibility of a structural engineer starts from the collection of sufficient information for the project to the execution of different activities on the construction site. In certain critical situations, they are responsible for material and equipment delivery for undergoing a special task of the construction project. They conduct frequent checks of the on-site labor works and the activities.

Training Works

Not all structural engineers are trained for the complete responsibilities. Some are gained through years of experience and some standard skills through different training activities. As construction is an industry prone to more of safety issues, structural engineers are to be trained for strict standards of working.

Organization authorities can train the structural engineers for special quality certifications or for special analysis or design software. Proper knowledge of the National codes of the area is an important technical knowledge for any structural engineer.

Roles and Responsibilities of a Consulting Civil Engineer

A consulting civil engineer is an independent, professional engineer who performs well-detailed engineering services for clients on agreed sum of money.

It is quite unfortunate that the services and responsibilities that a consulting civil engineer renders are poorly understood while those who seek to engage him have only a vague idea of his functions. Most graduates of engineering background also have a meager understanding of the role he plays. Even some consulting civil engineers lack adequate comprehension of their responsibilities and obligations.

This article is presented to address all of the above shortcomings and to make the public at large appreciate the works of a consulting civil engineer. I have drawn mostly on my experiences as a professional engineer who has worked with both governmental and corporate organizations on various landmark projects.

Consulting is not a field for a person who hesitates to face new challenges. The competent engineer who likes variety and enjoys the challenge of ever-changing problems can find a fascinating and rewarding career in a consulting firm.

The profession demands business and management skills in addition to engineering and professional trainings. It offers a unique opportunity for self-employment and it is perhaps the only path open to an engineer with the spirit of an entrepreneur who wishes to become his own boss in full-time engineering practice.

In spite of its importance, challenge and fascination, the profession of consulting engineering is little recognized and poorly appreciated by members of the public largely due to the fact that his services are seldom performed for individuals as in the case of other professions like medicine and law.

What is a Consulting Civil Engineer?

A consulting civil engineer is simply an independent, professional engineer who performs well-detailed engineering services for a client based on an agreed sum of money. He must be registered to practice as a professional engineer in the state or country where he resides and it is illegitimate for him to have commercial affiliations with manufacturers, material suppliers and contractors.

Services rendered by a given consulting civil engineer depend not only on his field of engineering but also on his choice between special and general practice.

Some consultants confine their activities to a limited field in which they function as specialists and thereby becoming consultants to other engineers or clients having need of highly specialized advice and guiding information. Others may prefer to specialize in services to a certain type of client rather than perform in a broader range.

Most consultants, however, offer broader services or general practice although their activities may be confined to one or more fields of engineering, or several types of projects. Such general practitioners are more likely to have several kinds of clients and therefore perform more varied services as they can handle all aspects of engineering projects.

Roles and Responsibilities of a Consulting Civil Engineer

The types of services performed by consulting civil engineers are outlined and discussed below.

Consultation

Consultation occurs when a client, who needs an opinion on some engineering problems, avails himself of the expert knowledge and the experience of a consulting civil engineer. Consultations may be brief or extended and may sometimes require considerable travel and a substantial portion of the consultant’s time.

Investigation

Most consultations usually require some study and investigation which involve analysis and simple computations while others may require field trips to observe and inspect equipment or structures. Still again, they may involve a review of studies, reports, investigations or communications prepared by other engineers or by the client’s management.

Feasibility Reports

These reports are concerned with determining the feasibility of some projects while presenting the results of surveys, studies and investigation carried out to confirm the engineering solution to be adopted in line with the financial cost. A feasibility study will usually include such items as purpose of study, requirements and needs of project, alternate solutions, estimated construction cost, recommendations and conclusion.

Engineering Design

Engineering design is the process of determining the physical characteristics and dimensions of a structure or project to be constructed or manufactured. These characteristics and dimensions are presented graphically on drawings, commonly referred to as blueprints by the layman. Such drawings, or plans, are supplemented by written documents called specifications.

Plans and Specifications are used to direct the contractor or the manufacturer on the details of work expected from him. Frequently, the design process includes the preparation of detailed lists of materials called bill of quantities which is used to procure all the materials needed for the construction or manufacturing work.

Procurement

The consulting civil engineer often assists the client in the selection of contractors or in the purchase of materials for the award of contracts. Procurement usually involves the receipt of a proposal from one or more material suppliers and selection is made on a competitive or a negotiated basis.

On construction projects, particularly for government organizations, contracts are usually awarded on the basis of competitive bidding while the engineer will normally prepare the contract documents in addition to drawings and specifications in conjunction with the client’s legal officer.

With the plans, specifications and contract documents, bids are solicited from contractors or manufacturers through public notices issued in accordance with legal requirements. After the receipt of all interested tenders, bids are opened publicly, as a rule, read and tabulated by the consulting civil engineer who will then makes his recommendations to the client.

Construction Supervision

This activity consists of two parts – general supervision and resident supervision. General supervision involves the following:

a) Periodic visits to site

b) Consultation with the Owner/Client

c) Interpretation of plans and specifications

d) Checking working drawings and data

e) Processing & certification of contractor’s payment estimates

f) Preparation of amendments to contractor’s contract

g) Final inspection of project

h) Preparation of “as-built” drawings

Resident supervision however requires the consulting engineer to send a representative or a resident engineer to the site of the project. The resident engineer is responsible for detailed supervision and inspection to ensure that the project is constructed according to the plans and specifications. In addition, he also coordinates and expedites the activities of the contractors.

Legal Services

Often consulting civil engineers are requested to function as expert witnesses in the court proceedings and to advise clients and lawyers on engineering matters involved in legal procedures.

Other Services

The list of services outlined above is by no means complete and a compilation of a complete list of services would be a formidable task and would serve no useful purpose. However, the listings given here adequately cover the range of services performed by a consulting civil engineer.

Roles and Responsibilities of a Civil Site Engineer

Roles and responsibilities of a civil site engineer depends on the nature of construction works in a project and involves various activities such as quality control and reporting.

As the activities carried out in a construction industry is highly dynamic in nature, different decisions and actions have to be carried out unexpectedly. These sudden actions are mostly carried out by the site in charge or the civil site engineer at construction site.

This means the roles and responsibilities of a civil site engineer is not specific for every construction site. These changes based on the activities and site conditions of the project. But in brief, the site engineer must possess certain basic roles and responsibilities for the execution and completion of the project.

Role and Responsibilities of a Civil Site Engineer

The site engineer should possess basic knowledge about the practical construction procedures in site, along with the details of how they are planned. This idea of planning and coordination will help him to have proper execution of the activities in the site with desired performance.

A site engineer is very essential for a construction project. The responsibilities of a site engineer are wide as he must provide sufficient advice and supervision when there are any technical issues, or for proper management and for the preparation of day to day reports of the construction works.

The responsibilities that is put on a site engineer in construction is mentioned briefly in below section:

1. Construction Site Responsibilities

The site engineer is the person who spends most of his time at the construction site compared with other managers or designers. Site engineers are updated daily about the coming day’s design and activities based on which he implements them at site.

The top members of the construction organization get a clear picture about the daily activities happening at the site through the site engineer.

2. Travelling

The site engineers are supposed to move from one site to another (based on the size of the project or number of projects) for any special needs. He must also be required to reach with the procurement of resources to get the materials as per the correct specifications if any discrepancies happen.

This means every sector of activities say its design, materials or execution, the site engineer has the role of advice.

3. Technical Activities

Site activities like establishment of the level and the survey control, which is required for the control of contracts must be performed by site engineer in required conditions. The works have to be set out as per the contract drawings. This requires checks at regular basis on the construction site.

The records maintained have to be accurate and they have to satisfy with the organizational and the legal requirements.

The site engineer has to face any unexpected difficulties raised from the technical side at any point of time. He must study the problem and resolve it in the most efficient manner as possible.

4. Preparation of Reports and Schedules

The site engineer is the one who have to ensure that the site have adequate resources to complete the tasks. This is conducted by having procurement schedules for the jobs carried out and liaise with the procurement department regarding the same.

A report on the future works to be carried out at site are prepared and produced by site engineers two weeks ahead. This is carried out in conjunction with the site agent.

The site engineer is responsible for keeping site diaries and the respective sheets for allocation.

5. Site Engineer for Health and Safety

For highly dangerous work site, the site engineer will take up the role of safety engineer. He has to ensure that the work carried out by the workers and other related activities are as per the safety regulation of the respective state or area.

Every construction organization must possess a safe working culture and practice. Its implementation and practice of following is supervised by the site engineers. There may be other safety, health officers for the organization, but ensuring safety is a common need.

Other responsibilities are to undergo construction activities that will promote the environmental compliance. Each work has to be carried out safely within the deadline.

6. Quality Assurance by Site Engineer

As we know, quality is a parameter that have to be kept in practice from the initial stage of planning to the end of the project. The major issues with design and documentation can be corrected during the construction by the site engineer based on advice from the structural engineers.

Any undesirable activities in construction brings high loss of quality and money. The site engineer assures quality by the following means:

Promoting the best construction practices
Undergo activities and practices that comply with the procedures of the company and the specification.
Assures the work is completed and delivered without any defect and delay
One must highlight value engineering opportunities

7. Communication and leadership duties

As the site engineer have to know the technical details from the above levels and make it in practice in the site, he must be efficient enough to coordinate the information that is communicated. He must take up the detail from the higher levels accurately and pass them to the below contractors, supervisors or labor workers. It not how efficiently you as a site engineer understand the idea, but it’s on how you convey it to your sub-workers. This will reflect to have the need for leadership quality to convey and make the workers do the work.